In conventional "air-bearing" rotating rigid disk files, each of the read/write transducers (or heads) is supported on a carrier (or slider) which rides on a cushion or bearing of air above the surface of its associated disk when the disk is rotating at its operating speed. The slider is connected to a linear or rotary actuator by means of a relatively fragile suspension. There may be a stack of disks in the disk file with the actuator supporting a number of sliders. The actuator moves the sliders generally radially so that each head may access the recording area of its associated disk surface. In these conventional disk files the slider is connected to a suspension and is either biased towards the disk surface by a small force from the suspension or is "self-loaded" to the disk by means of a "negative pressure" air-bearing surface. The slider is typically in contact with the disk surface only during start and stop operations; i.e., from the time the disk file is turned on until the disk reaches a speed sufficient to cause the slider to ride on the air-bearing, and again when the disk file is turned off and the rotational speed of the disk falls below that necessary to create the air-bearing.
The conventional head used for reading and writing data on thin film disks in air-bearing disk files is a dual function inductive read/write head. Because such a head must be able to both read and write data, trade-offs must be made in the design of the head and disk parameters in order to optimize both the read and write data signals in the disk drive. In order to overcome this disadvantage, magnetoresistive (MR) read sensors (or heads), which generate a read signal as a result of a change in electrical resistance caused by the magnetic fields recorded on the disk, have been proposed to be used with inductive write heads in air-bearing disk files. By way of example, assignee's U.S. Pat. No. 3,908,194 describes a "piggyback" thin film head which combines an MR read head and an inductive write head. The first commercial air-bearing rigid disk file with an MR read head and an inductive write head was the IBM "Corsair" disk drive available in 1991.
It has been known since the early days of magnetic recording that "contact" recording is desirable because the amplitude of the read signal from the disk decreases with increasing head-disk spacing. Thus, in addition to the above-described conventional air-bearing disk files, "contact" recording rigid disk files have been proposed.
In one type of contact recording, referred to as "liquid-bearing" contact recording, the head-disk interface includes a liquid film as a liquid bearing between the transducer carrier and the disk. There are several references which describe different types of liquid-bearing disk files. In assignee's U.S. Pat. No. 2,969,435, a sled-type transducer carrier with a large flat surface rides on a layer of oil on the disk, the oil being supplied from an oil reservoir external to the disk file and discharged from a nozzle located ahead of the carrier. Other examples of liquid-bearing contact recording disk files are described in assignee's pending application, U.S. Ser. No. 264,604, now abandoned, filed Oct. 31, 1988, and published May 9, 1990 as European published application EP 367510, and in U.S. Pat. No. 5,097,368, filed Dec. 20, 1989. In these types of liquid-bearing disk files a liquid is continuously recirculated throughout the disk file to maintain a relatively thick liquid film on the disk, and the head carrier has a plurality of pads which plow through the liquid film as the disk rotates. More recently, in assignee's copending application U.S. Ser. No. 07/724,646, now U.S. Pat. No. 5,202,803, a liquid-bearing disk file has been described wherein a relatively thin lubricant film is maintained on the disk and a transducer carrier, having specially adapted pads or "ski feet", rides on the surface of the liquid film as the disk rotates. When the disk file reaches operating speed, the forward portion of the transducer carrier is raised above the liquid film due to an air-bearing effect, while the rear pad or ski foot rides on the surface of the liquid film.
In another type of contact recording, referred to as "dry" contact recording, the disk file uses an integrated head-suspension which makes physical contact with the disk surface during read and write operations. In this type of head-suspension, as described for example in U.S. Pat. No. 5,041,932, a portion of the head wears away due to frictional contact with the disk over the life of the disk file. Another type of "dry" contact recording disk file, as described in assignee's U.S. Pat. No. 4,819,091 utilizes a wear-resistant single crystal head carrier which is maintained in contact with the disk by means of an attractive force generated by the frictional contact between the carrier and the rotating disk. While these types of contact recording disk files are referred to as "dry", it is possible to also utilize a thin liquid lubricant film on the disk, even though this film may not function as a liquid bearing in the same manner as for liquid-bearing contact recording disk files.
In all of these contact recording techniques for rigid disk files, the head may not always be in physical contact with the actual surface of the rigid disk because of the presence of a liquid film and/or because the head carrier may periodically skip or fly over the disk surface. Nevertheless, for purposes of the present invention, the term "contact" recording in rigid disk files shall include these types of "near contact" recording as well.
None of the proposed contact recording techniques contemplate the use of an MR read sensor, or suggest any means to incorporate an MR read sensor, and its associated benefits, into a disk file which has a head carrier maintained in contact with the disk during read and write operations. Thus what is needed is a contact recording disk file which utilizes an MR read sensor.